US3517557A - Device for sampling hot gaseous mixtures containing condensables - Google Patents

Description

v June 30, 1970 CNGRIANGER ET AL 3,517,557

DEVICE FOR SAMPLING HOT GASEOUS MIXTURES CONTAINING CONDENSABLES Filed Nov. 27, 1968 V Z 4 11 y x f3 \g Z Ail/ I Q v: g I v N Pm JL.

INVENTORS Camille Granger Marc Demeure, Michel Bruder A v a q'ys United States Patent 3,517,557 DEVICE FOR SAMPLING HOT GASEOUS MIX- TURES CONTAINING CONDENSABLESv Camille Granger and Marc Demeure, Martigues, and Michel Bruder, Vaucrcsson, France, assignors to Naphtachimie, Societe Anonyme, Paris, France Filed Nov. 27, 1968, Ser. No. 779,514 Claims priority, applicatiog9grance, Nov. 30, 1967,

Int. 01. (0111 1/22 US. Cl. 73-4215 8 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a device for taking samples of a circulating gaseous mixture containing readily condensable components and more particularly to a device for the discontinuous sampling of gaseous mixtures of the type issuing at high temperature from thermal cracking ovens.

The operation of taking samples from gaseous mixtures of this nature represents a diflicult problem. The sampling is addressed to the taking of gaseous mixtures circulating at high temperatures, such as of the order of 400 C. and under a pressure generally less than 1 kg./ sq. cm., in which the gaseous mixtures are made up of water vapor, light hydrocarbons and heavy oils, tars and carbon, all of which are easily condensable, consequently entailing the danger of blocking the pipes of the sampling device.

It is known that samples may be taken from gaseous mixtures issuing from cracking ovens by processes which generally comprise cooling the samples by washing with water in order to eliminate the easily condensable fractions as soon as the samples have been drawn off. This manner of operation prevents troublesome condensation in the pipes through which the gaseous mixture is conveyed to the apparatus for analysis. The major disadvantage of such processes is that the composition of the gaseous mixture analyzed differs considerably from that of the mixture circulating through the system of pipes from which the samples are taken.

It is also known that samples which are drawn off can be diluted in an auxiliary gas, such as hydrogen, at the very moment at which they are taken. In this way, the troublesome condensation phenomena can be minimized in the system of pipes through which the samples are conveyed. On the other hand, analysis of the diluted samples, as by chromatography, is necessarily imprecise. In addition, it appears that the concentration of these samples in the auxiliary gas cannot easily be maintained constant from one sample to the other by reason of variations in pressure in the tube from which the sample is taken or fouling of the sampler, for example.

The present invention has for its object the elimination of the disadvantages of the above described processes and the provision of a device from which accurate samples can be taken for analysis without fear of blocking the passages of the device with condensable material.

These and other objects and advantages of this invention will hereinafter appear and for purposes of illustration, but not of limitation, an embodiment of the invention is shown in the accompanying drawing.

The invention comprises a device in which the dangers of .blockage are limited and which permits highly representative samples of a gaseous mixture, circulating at high temperature through a system of pipes, to be drawn OE and analyzed. The device comprises a sampler, one end of which extends into the system of pipes while the other end is connected to a circuit housed within a chamber maintained atconstant temperature of at least 150 C., in which the circuit comprises a sampling valve intended periodically to isolate a sample of the gaseous mixture of given volume which sample is entrained out of the chamber in a stream of inert gas.

The sample which is thus entrained can be cooled to a relatively high degree and circulated through pipes without further risk of condensation. It can therefore be easily conveyed to the analyzing device or devices, such as a chromatograph, which can be located in a convenient site distant from the point at which the sample has been taken.

In accordance with the practice of this invention, the temperature of the chamber, in which the circuit embodying the sampling valve is placed, should be as high as possible in order to restrict condensation of the heavy products contained in the drawn off gaseous mixture. In practice, it is preferred to operate the chamber at a temperature of at least 200 C. but it is seldom desirable to exceed 250 C. since the sampling valves currently employed are not generally satisfactory above such temperatures.

The drawing is an illustration, in diagrammatic form, of a sampling device embodying the features of this invention comprising a dismantleable sampler 1, in the form of a tubing, mounted for connection with a tube 2 contiguous to a system of pipes 3 through which the gaseous mixture to be tested, such as that issuing from a cracking furnace, circulates at a temperature in the vicinity of 400 C., under relative pressure of approximately 600 g./sq. cm. Insulation 4 is used thermally to line the system of pipes 3 and the connecting tube 2 through which the sampler 1 extends.

The sampler 1 is dismantleable in that it can slide along the axis of the connecting tube 2 with the assembly being sealed by a stuffing' box 5. A valve with integral passage 6 permits the installation to be isolated when the sampler is dismantled and can be closed before the sampler is completely extracted from the connecting tube 2.

Continuous injection of water vapor into the portion of the connecting tube 2 between the valve 6 and the stufl'ingbox 5, as by means of a pipe 7, prevents internal fouling of the connecting tube 2. Another water vapor intake pipe 8, having a valve 9, connects with the sampler 1, for circulation of water vapor through the interior of the sampler during the periods of time other than that at which gaseous mixture issuing from the system of pipes 3 is drawn oflf.

The sampler 1 is connected to a circuit housed in a chamber 10 maintained at constant temperature, such as at a temperature within the range of 200 to 250 C., by suitable heating means such as a heating coil 11. The sampler can be isolated from the circuit by means of the valve 12. The circuit comprises a separator 13 of the cyclone type and a filter 14 which separate condensed products or solid particles which might be contained in the gaseous mixture and the circuit is completed with a sampling valve 15 of a well known type which can operate at high temperature. A vent 16 communicates with the valve 15 to permit samples of constant volume to be measured under atmospheric pressure. Conduits 17 and 18 communicate the sampling valve to a chromatograph, the sample being conveyed by entrainment in a carrier gas which may be hydrogen, helium or nitrogen, for example. In order to take a sample, vapor intake valve 9 is closed and valve 12 is opened. The gaseous mixture to be analyzed is then free to pass through the sampler. Condensed products and carbon dust contained in the gaseous mixture are removed by the cyclone separator 13 and the filter 14 and the gaseous mixture then passes through the sample valve 15 by means of which a given volume of gas is isolated and directed through pipe 18 to the chromatograph after entrainment with carrier gas which is introduced through pipe 17.

As soon as the sample has been isolated by the sampling valve 15, valve 12 is closed and valve 9 is opened whereby water vapor passes as a stream from line 8 through the interior of the sampler for cleaning the interior thereof.

The sampling device of this invention can be provided with valves which are capable of automatic control by a programmer to permit samples of constant volume to be taken at regular timed intervals and for passage immediately to an apparatus for analysis automatically as by chromatography.

It will be apparent from the foregoing that we have provided a new and improved self-cleaning sampling device for hot gaseous mixtures whereby condensations which might otherwise cause blockage is substantially eliminated.

It will be understood that changes may be made in the details of construction and operation without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. A device for the periodic sampling of a stream of a hot gaseous mixture containing easily condensable components comprising a housing, heating means for maintaining the housing at a temperature of at least 150 C., a circuit within said heated housing including a sampling device operative periodically to remove a sample of hot gaseous mixture of given volume, a sampling tube one end of which communicates with the gaseous stream and the other end with the sampling device, means connecting the sampling device within the housing for entrainment of the sample of gaseous material with an inert gas, said sampling tube and sampling device maintaining said hot gas at an elevated temperature above the condensing temperature of its components prior to reaching said housing and while within said housing and means connecting the sampling device for transmission of the gaseous material diluted with the inert gas to a gas test means.

2. A device as claimed in claim 1 in which the housing is maintained at a temperature within the range of 200 to 250 C.

3. A device as claimed in claim 1 in which the hot gaseous mixture circulates through a system of pipes and in which the device includes a tube which extends into communication with the system of pipes, a valve within said tube for isolating the system of pipes from the outside atmosphere, and a stuffing box enclosing the tube with means for insertion of the sampling tube therethrough into communication with the system of pipes.

4. A device as claimed in claim 1 in which the circuit includes a conduit in communication with the sampler tube in advance of the sampling device, a source of water vapor, and valve means for controlling the passage of water vapor through the sampler tube when the sampler is not being used for the removal of a sample of the gaseous mixture.

5. A device as claimed in claim 3 which includes a conduit in communication with the tube, a source of water vapor and a valve means in the conduit for controlling the passage of water vapor into the tube.

6. A device as claimed in claim 1 in which the circuit within the housing includes a cyclone separator in line with the sampler tube in advance of the sampling device for removal of solids and condensate from the gaseous mixture.

7. A device as claimed in claim 1 in which the circuit within the housing includes a filter in line with the sampler tube and in advance of the sampling device for the removal of solids from the gaseous mixture.

8. A device as claimed in claim 1 which includes a valve in line with the sampler tube in advance of the sampling device for isolating the sampler tube from the circuit.

References Cited UNITED STATES PATENTS 2,930,237 3/1960 Fowler et al.

2,964,938 12/1960 Fuller 7342l.5 XR 3,043,145 7/1962 Hoffman 73421.5 3,053,077 9/1962 Tracht 7323 3,255,575 6/1966 Roberts 73-422 XR FOREIGN PATENTS 1,499,984 11/ 1967 France.

S. CLEMENT SWISHER, Primary Examiner H. C. POST III, Assistant Examiner

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